Red-eye is a phenomenon in flash photography where a flash is reflected within a subject's eye and appears in a photograph as a red dot where the black pupil of the subject's eye would normally appear. The unnatural glowing red of an eye is due to internal reflections from the vascular membrane behind the retina, which is rich in blood vessels. This objectionable phenomenon is well understood to be caused in part by a small angle between the flash of the camera and the lens of the camera. This angle has decreased with the miniaturization of cameras with integral flash capabilities. Additional contributors include the relative closeness of the subject to the camera and ambient light levels.
Digital cameras are becoming more popular and smaller in size. U.S. Pat. No. 6,407,777 to DeLuca describes a method and apparatus where a red eye filter is digitally implemented in the capture device. The success or failure of such filter relies on the quality of the detection and correction process.
Most algorithms that involve image analysis and classification, are statistical in nature. There is therefore a need to develop tools which will improve the probability of successful detection, while reducing the probability of false detection, while maintaining optimal execution, especially in limited computational devices such as in digital cameras. In many cases knowledge of the image characteristics such as image quality may affect the design parameters and decisions the detection and correction software needs to implement. For example an image with suboptimal exposure may deteriorate the overall detection of red-eye defects.
Thus, what is needed is a method of improving the success rate of algorithms for detecting and reducing red-eye phenomenon.